Stable carbon isotope biogeochemistry of a shallow sand aquifer contaminated with fuel hydrocarbons |
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| Institution: | 1. Departamento de Física Matemática y de Fluidos, UNED, Senda del Rey 9, Madrid 28040 Spain;2. ETSIAE, Universidad Politécnica de Madrid, Plaza Cardenal Cisneros 3, Madrid 28040 Spain;1. Department of Imaging and Applied Physics, Curtin University, GPO Box U 1987, Perth 6845, Western Australia, Australia;2. Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark;3. Environmental Measurement and Analysis Center, National Institute of Environmental Research, Environmental Research Complex, Kyungseo-dong, Seo-gu, Incheon 404-170, Republic of Korea;4. Department of Ocean Sciences, Inha University, 100 Inha-ro, Nam-gu, Incheon 402-751, Republic of Korea;5. Key Laboratory of Coast and Island development of Ministry of Education, School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China;6. Department of the Environment, Australian Antarctic Division, Channel Highway, Kingston 7050, Tasmania, Australia;7. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart 7001, Tasmania, Australia |
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| Abstract: | Ground-water chemistry and the stable C isotope composition (δ13CDIC) of dissolved inorganic C (DIC) were measured in a sand aquifer contaminated with JP–4 fuel hydrocarbons. Results show that ground water in the upgradient zone was characterized by DIC content of 14–20 mg C/L and δ13CDIC values of −11.3‰ to −13.0‰. The contaminant source zone was characterized by an increase in DIC content (12.5 mg C/L to 54 mg C/L), Ca, and alkalinity, with a significant depletion of 13C in δ13CDIC (−11.9‰ to −19.2‰). The source zone of the contaminant plume was also characterized by elevated levels of aromatic hydrocarbons (0 μg/L to 1490 μg/L) and microbial metabolites (aromatic acids, 0 μg/L to 2277 μg/L), non-detectable dissolved O2, NO3 and SO4. Phospholipid ester-linked fatty acid analyses suggest the presence of viable SO4-reducing bacteria in ground water at the time of sampling. The ground-water chemistry and stable C isotope composition of ground-water DIC are interpreted using a chemical reaction model involving rainwater recharge, contributions of CO2 from soil gas and biodegradation of hydrocarbons, and carbonate dissolution. The major-ion chemistry and δ13CDIC were reconciled, and the model predictions were in good agreement with field measurements. It was concluded that stable C isotope measurements, combined with other biogeochemical measures can be a useful tool to monitor the dominant terminal electron-accepting processes in contaminated aquifers and to identify mineralogical, hydrological, and microbiological factors that affect δ13C of dissolved inorganic C. |
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